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List of earthquakes in California

From Wikipedia, the free encyclopedia

Probabilistic seismic hazard map

The earliest known earthquake in the U.S. state of California was documented in 1769 by the Spanish explorers and Catholic missionaries of the Portolá expedition as they traveled northward from San Diego along the Santa Ana River near the present site of Los Angeles. Ship captains and other explorers also documented earthquakes. As Spanish missions were constructed beginning in the late 18th century, earthquakes records were kept. After the missions were secularized in 1834, records were sparse until the California Gold Rush in the 1840s. From 1850–2004, there was about one potentially damaging event per year on average, though many of these did not cause serious consequences or loss of life.[1][2]

Since the three damaging earthquakes that occurred in the American Midwest and the East Coast (1755 Cape Ann, 1811–12 New Madrid, 1886 Charleston) were well known, it became apparent to settlers that the earthquake hazard was different in California. While the 1812 San Juan Capistrano, 1857 Fort Tejon, and 1872 Owens Valley shocks were in mostly unpopulated areas and only moderately destructive, the 1868 Hayward event affected the thriving financial hub of the San Francisco Bay Area, with damage from Santa Rosa in the north to Santa Cruz in the south. By this time, scientists were well aware of the threat, but seismology was still in its infancy. Following destructive earthquakes in the late 19th and early 20th centuries, real estate developers, press, and boosters minimized and downplayed the risk of earthquakes out of fear that the ongoing economic boom would be negatively affected.[3][4]

California earthquakes (1769–2000)

According to seismologist Charles Richter, the 1906 San Francisco earthquake moved the United States Government into acknowledging the problem. Prior to that, no agency was specifically focused on researching earthquake activity. The United States Weather Bureau did record when they happened and several United States Geological Survey scientists had briefly disengaged from their regular duties of mapping mineral resources to write reports on the New Madrid and Charleston events, but no trained geologists were working on the problem until after 1906 when the Coast and Geodetic Survey was made responsible. The outlook improved when Professor Andrew Lawson brought the state's first monitoring program online at the University of California, Berkeley in 1910 with seismologist Harry Wood, who was later instrumental in getting the Caltech Seismological Laboratory in Pasadena operational in the 1920s.[3][5]

Early developments at the Caltech lab included an earthquake observation network using their own custom-built short-period seismometers, the Richter magnitude scale, and the Modified Mercalli intensity scale (an updated version of the Mercalli intensity scale). In 1933, the Long Beach earthquake occurred in a populated area and damaged or destroyed many public school buildings in Long Beach and Los Angeles. Some decades later, the San Fernando earthquake affected the San Fernando Valley north of Los Angeles with heavy damage to several hospitals. In both cases, the perception of California policy makers changed, and state laws and building codes were modified (with much debate) to require commercial and residential properties to be built to withstand earthquakes. Higher standards were established for fire stations, hospitals, and schools, and construction of dwellings was also restricted near active faults.[4][5]

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Tectonic setting

During the last 66 million years, nearly the entire west coast of North America was dominated by a subduction zone, with the Farallon Plate subducting beneath the North American Plate. Presently, the Juan de Fuca Plate (with its Explorer and Gorda satellite plates) and the Rivera and Cocos Plates are the only remnants of the once much larger Farallon Plate. The plate margin that remains in California is that of the strike-slip San Andreas Fault (SAF), the diffuse Pacific–North American plate boundary that extends east into the Basin and Range Province of eastern California and western Nevada (a seismically active area called Walker Lane) and southwest into the California Continental Borderland region off the central and southern coasts. This system of faults terminates in the north at the Mendocino Triple Junction, one of the most seismically active regions in the state, where earthquakes are occasionally the result of intraplate deformation within the Gorda Plate. It terminates in the south at the Salton Sea where displacement transitions to a series of spreading centers and transform faults, beginning with the Brawley Seismic Zone in the Imperial Valley.[6]

In the San Francisco Bay Area, the San Andreas system of faults spans offshore and into the East Bay area, with the bulk of the faults lying to the east of the main SAF. There is a 70% probability that one of these faults will generate a 6.7 Mw or greater earthquake before 2030, including the Hayward Fault Zone, which has gone beyond its average return period of 130 years (154 years ago as of September 2023). While the SAF is quiet north of San Francisco , the central SAF segment near San Juan Bautista is where aseismic creep was first studied, and to the south is where the recurring Parkfield earthquakes occur. The secondary faults lay to the west of the main SAF at the extreme southern portion, including the active and young San Jacinto Fault Zone, which may be taking over as the primary boundary south of Cajon Pass. A paleoseismic investigation using Lidar revealed that more than 16 feet (5 m) of slip has accumulated since the 1857 event on the southern SAF, which borders the Mojave Desert to the north and east of the Greater Los Angeles Area. Near the Transverse Ranges, reverse and thrust faults have produced damaging earthquakes in Santa Barbara and the San Fernando Valley.[6]

Notable earthquakes

Date Name Area Mag. MMI Deaths Injuries Total damage Notes
2022-12-20 Humboldt County North Coast 6.4 Mw VIII 2 17
2019-07-05 Ridgecrest Eastern 7.1 Mw IX 5 $5.3bn Doublet
2019-07-04 Ridgecrest Eastern 6.4 Mw VIII 1 20 $5.3bn Doublet
2014-08-24 South Napa North Bay 6.0 Mw VIII 1 ~200 $362M–$1bn
2014-03-28 La Habra LA Area 5.1 Mw VII Few $10.8M [7]
2010-04-04 Baja California Baja California 7.2 Mw VII 2–4 100–233 $1.15bn
2010-01-09 Eureka North Coast 6.5 Mw VI 35 $21.8–43M
2008-07-29 Chino Hills LA Area 5.4 Mw VI 8 Limited
2007-10-30 Alum Rock Bay Area 5.6 Mw VI Limited
2003-12-22 San Simeon Central Coast 6.6 Mw VIII 2 40 $250–300M
2000-09-03 Yountville North Bay 5.0 Mw VII 41 $10–50M
1999-10-16 Hector Mine Eastern 7.1 Mw VII 4–5 Limited
1994-01-17 Northridge LA Area 6.7 Mw IX 57 8,700+ $13–40bn
1992-06-28 Big Bear Inland Empire 6.5 Mw VIII 63 More than $60M Triggered
1992-06-28 Landers Inland Empire 7.3 Mw IX 3 400+ $92M
1992-04-26 Cape Mendocino North Coast 6.6 Mw VIII Some Triggered
1992-04-26 Cape Mendocino North Coast 6.5 Mw VIII Some Triggered
1992-04-25 Cape Mendocino North Coast 7.2 Mw IX 98–356 $48–75M Tsunami
1992-04-22 Joshua Tree Inland Empire 6.3 Ms VII 32 Light–moderate [7]
1991-06-28 Sierra Madre LA Area 5.6 Mw VII 2 100–107 $34–40M
1990-02-28 Upland LA Area 5.7 Mw VII 30 $12.7M
1989-10-17 Loma Prieta Santa Cruz Mts 6.9 Mw IX 63 3,757 $5.6–6bn Tsunami
1989-08-08 Loma Prieta Santa Cruz Mts 5.4 ML VII 1 Minor
1987-11-24 Elmore Ranch Imperial Valley 6.5 Mw VIII 2 90+ Triggered [8]
1987-11-23 Superstition Hills Imperial Valley 6.1 Mw VIII $3M [8]
1987-10-01 Whittier LA Area 5.9 Mw VIII 8 200 $213–358M
1986-07-21 Chalfant Valley Eastern 6.2 Mw VI 2 $2.7M Sequence
1986-07-13 Oceanside South Coast 5.8 Mw VI 1 $700k [9]
1986-07-08 N. Palm Springs Inland Empire 6.0 Mw VII 29–40 $4.5–6M
1984-04-24 Morgan Hill South Bay 6.2 Mw VIII 21–27 $7.5–8M
1983-05-02 Coalinga Central Valley 6.2 Mw VIII 94 $10M
1981-04-26 Westmorland Imperial Valley 5.9 Mw VII $1–3M [10]
1980-11-08 Eureka North Coast 7.3 Mw VII 6 $2–2.75M
1980-05-25 Mammoth Lakes Eastern 6.2 Mw VII 9 $1.5M Swarm[11]
1980-01-26 Livermore East Bay 5.4 Mw VII Doublet [12]
1980-01-24 Livermore East Bay 5.8 Mw VII $11.5M Doublet [13]
1979-10-15 Imperial Valley Imperial Valley 6.4 Mw IX 91 $30M
1979-08-06 Coyote Lake South Bay 5.7 Mw VII 16 $500k
1978-08-13 Santa Barbara Central Coast 5.8 Mw VII 65 $12M [14]
1975-08-01 Butte County Butte County 5.7 ML VIII 10 $3M [7]
1973-02-21 Point Mugu South Coast 5.8 Mw VII Several $1M
1971-02-09 San Fernando LA Area 6.6 Mw XI 58–65 200–2,000 $505–553M
1969-10-01 Santa Rosa North Bay 5.7 Mw VIII Doublet
1969-10-01 Santa Rosa North Bay 5.6 Mw VII 1 $8.35M Doublet
1968-04-08 Borrego Mtn Imperial Valley 6.5 Mw VII Some Rockslides [15]
1957-03-22 San Francisco Bay Area 5.7 Mw VII 1 40 $1M
1954-12-21 Eureka North Coast 6.5 ML VII 1 Several $2.1M [16]
1952-08-22 Kern County Central Valley 5.8 Mw VIII 2 Several $10M
1952-07-21 Kern County Central Valley 7.3 Mw XI 12 Hundreds $60M
1948-12-04 Desert Hot Springs Inland Empire 6.4 Mw VII Several Minor
1941-11-14 Torrance–Gardena LA Area 5.4 Ms VIII $1.1M [17]
1941-06-30 Santa Barbara Central Coast 5.9 Mw VIII $100k [18]
1940-05-18 El Centro Imperial Valley 6.9 Mw X 9 20 $6M
1933-03-10 Long Beach South Coast 6.4 Mw VIII 115–120 $40M
1932-06-06 Eureka North Coast 6.4 Mw VIII 1 3 Severe
1927-11-04 Lompoc Central Coast 7.3 Mw Moderate Tsunami [19]
1925-06-29 Santa Barbara Central Coast 6.8 Mw IX 13 $8M
1923-01-22 Humboldt County North Coast 7.2 Ms Severe Tsunami [20]
1920-06-21 Inglewood LA Area 4.9 ML VIII More than $100k [21]
1918-04-21 San Jacinto Inland Empire 6.7 Mw IX 1 Several $200k
1915-06-22 Imperial Valley Imperial Valley 5.5 Mw VIII 6 $900k Doublet [22]
1906-04-18 San Francisco NorthernCentral 7.9 Mw XI 700–3,000+ Conflagration / tsunami
1899-12-25 San Jacinto Inland Empire 6.7 Mw IX 6 $50k or more [23]
1898-03-30 Mare Island North Bay 5.8–6.4 Mw VIII–IX $350k
1892-04-21 Vacaville–Winters Central Valley 6.2 MLa IX Doublet
1892-04-19 Vacaville–Winters North Bay 6.4 MLa IX 1 $225–250k Doublet
1892-02-23 Laguna Salada Baja California 7.1–7.2 Mw VIII Moderate
1873-11-23 Crescent City North Coast 6.7 MLa VIII Some Ground cracks [24]
1872-03-26 Owens Valley Eastern 7.4–7.9 Mw X 27 56 $250k
1868-10-21 Hayward Bay Area 6.3–6.7 Mw IX 30 $350k
1865-10-08 Santa Cruz Mts Santa Cruz Mts 6.3 MLa VIII $500k [25]
1857-01-09 Fort Tejon CentralSouthern 7.9 Mw IX 2 Severe
1838-06-?? San Andreas Bay Area 6.8–7.2 Mw VIII Minor
1812-12-21 Ventura Central Coast 7.1 MLa VIII 1 Tsunami [26]
1812-12-08 San Juan Capistrano South Coast 6.9–7.5 VII–IX 40 Moderate
Stover & Coffman 1993 uses various seismic scales. Mla is a local magnitude that is equivalent to ML (Richter magnitude scale) and is used for events that occurred prior to the instrumental period. It is based on the area of perceptibility (as presented on isoseismal maps). Mw = moment magnitude scale and Ms = surface wave magnitude. The inclusion criteria for adding events are based on WikiProject Earthquakes' notability essay that was developed for stand alone articles. The principles described are also applicable to lists. In summary, only damaging, injurious, or deadly events should be recorded.
k= thousand, M = million, bn = billion

See also


  1. ^ Toppozada, T. R.; Branum, D. (2004), "California earthquake history", Annals of Geophysics, 47 (2–3): 509–512
  2. ^ Ellsworth, W. L. (1990), "Earthquake history, 1769–1989", The San Andreas Fault System, California – USGS Professional Paper 1515, United States Geological Survey, pp. 156, 157, ISBN 978-0607716269
  3. ^ a b Hough, S. E. (2007), "Richter's Scale: Measure of an Earthquake, Measure of a Man", Physics Today, Princeton University Press, 61 (1): 51–61, Bibcode:2008PhT....61a..60H, doi:10.1063/1.2835157, ISBN 978-0691128078
  4. ^ a b Geschwind, C. (2001). California Earthquakes: Science, Risk, and the Politics of Hazard Mitigation. Johns Hopkins University Press. pp. 3–22, 105–114, 165, 181. ISBN 978-0801865961.
  5. ^ a b Goodstein, J. R. (2006), Millikan's School: A History of the California Institute of Technology, W.W. Norton & Company, pp. 125–152, ISBN 978-0393329988
  6. ^ a b Yeats, R. (2012), Active Faults of the World, Cambridge University Press, pp. 19, 80–83, 89–94, 96–114, ISBN 978-0521190855
  7. ^ a b c National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Database (Data Set), National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K
  8. ^ a b Stover & Coffman 1993, pp. 98, 179, 180
  9. ^ Stover & Coffman 1993, pp. 97, 177
  10. ^ Stover & Coffman 1993, pp. 96, 168, 169
  11. ^ Stover & Coffman 1993, pp. 95, 168
  12. ^ Stover & Coffman 1993, pp. 95, 166, 167
  13. ^ Stover & Coffman 1993, pp. 94, 166, 167
  14. ^ Stover & Coffman 1993, pp. 94, 163
  15. ^ Stover & Coffman 1993, pp. 91, 154
  16. ^ Stover & Coffman 1993, pp. 88, 148
  17. ^ Stover & Coffman 1993, pp. 82, 137
  18. ^ Stover & Coffman 1993, pp. 82, 136
  19. ^ Stover & Coffman 1993, pp. 77, 128
  20. ^ Stover & Coffman 1993, pp. 77, 125
  21. ^ Stover & Coffman 1993, pp. 76, 124
  22. ^ Stover & Coffman 1993, pp. 76, 121
  23. ^ Stover & Coffman 1993, pp. 74, 113
  24. ^ Stover & Coffman 1993, pp. 73, 108
  25. ^ Stover & Coffman 1993, pp. 73, 104
  26. ^ Stover & Coffman 1993, pp. 72, 100


Further reading

External links

This page was last edited on 7 September 2023, at 20:38
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